You must register for Medicare during specific windows, or you may pay higher premiums for life

Most people become may be able to access for Medicare at age 65. You do not automatically enroll — you must sign up yourself during your Initial Enrollment Period, which runs for seven months: three months before the month you turn 65, the month you turn 65, and three months after. If you miss this window, you will owe a permanent penalty on your Part B and Part D premiums unless you have a valid reason for the delay.

The rules differ slightly depending on whether you are still working, whether your employer offers health insurance, and whether you are already receiving Social Security. This guide explains the timelines, what happens if you miss a important date, and how to register.

Key Takeaways

  • Your Initial Enrollment Period is seven months long: three months before you turn 65, the month of your birthday, and three months after.
  • If you are still working and covered by your employer's health plan, you may delay Part B enrollment without penalty, but you must enroll in Part A at 65.
  • Missing your enrollment window triggers a permanent 10% increase to your Part B premium and 1% per month increase to your Part D premium, even if you enroll later.
  • You can register online at Medicare.gov, by phone at 1-800-MEDICARE, or in person at your local Social Security office.
  • If you turn 65 while still employed, ask your employer's benefits department whether you should delay Part B or enroll when ready.

Your seven-month Initial Enrollment Period explained

Your Initial Enrollment Period begins three months before the month you turn 65 and ends three months after. For example, if you turn 65 in June, your enrollment period runs from March through September. You can register at any point during those seven months, and coverage will begin on the first day of the month you turn 65 (or the first day of the following month if you enroll after your birthday month).

The Social Security Administration handles Medicare enrollment. You do not need to wait until you receive your first Social Security check — enrollment and benefit payments are separate. Even if you plan to delay Social Security, you still need to register for Medicare at 65 to avoid penalties.

What happens if you miss your Initial Enrollment Period

If you do not register during your seven-month window, you will owe a late enrollment penalty for as long as you have Medicare. For Part B, the penalty is 10% of the standard premium for each full year you were may be able to access but not enrolled. For Part D (prescription drug coverage), the penalty is 1% of the national average premium for each month you were may be able to access but not enrolled. These penalties are permanent — they do not go away even after you eventually enroll.

The only exception is if you had creditable coverage — health insurance through an employer, a spouse's employer, or TRICARE (military coverage) — that was at least as good as Medicare. If you can show you had such coverage when you turned 65, you may avoid the penalty. You will need to provide documentation from your former employer or insurance company, so keep those records.

Special rules if you are still working at 65

If you are still employed and your employer offers health insurance, you may delay Part B enrollment without penalty. However, you must still enroll in Part A (hospital insurance) at 65, even if you do not use it. Part A has no monthly premium for most people, so there is no cost to registering.

Once you leave your job or your employer coverage ends, you have eight months to enroll in Part B without penalty. This is called your Special Enrollment Period. You will need to show proof that you had employer coverage — usually a letter from your employer's benefits department stating the coverage dates and that it was group health insurance. Without this proof, you may owe the late enrollment penalty.

If your employer has fewer than 20 employees, different rules explore, and Medicare becomes your primary insurance at 65. Ask your employer's benefits department whether you should enroll in Part B when ready or whether you can delay.

How to register for Medicare

You have three ways to register: online, by phone, or in person. The online method is fastest. Go to Medicare.gov, click "Sign Up for Medicare," and create an account using your Social Security number, date of birth, and contact information. You can complete the entire process in about 10 minutes. Coverage typically begins the first of the month you turn 65 or the first of the following month, depending on when you enroll.

To register by phone, call 1-800-MEDICARE (1-800-633-4227). Representatives are available Monday through Friday, 8 a.m. to 8 p.m. Eastern time. Have your Social Security number, date of birth, and information about any current health coverage ready. The call usually takes 15 to 20 minutes.

You can also visit your local Social Security office in person. Find the nearest office at ssa.gov/locator. Bring your Social Security card, proof of citizenship or legal residency (passport or birth certificate), and proof of age. Processing in person may take longer, but you will receive a receipt when ready.

Enrolling in Part D (prescription drug coverage) on time

Part D enrollment follows the same Initial Enrollment Period as Part B. You must enroll during your seven-month window or pay a permanent penalty. Unlike Part B, there is no employer exception — if your employer does not offer prescription drug coverage that is at least as good as Medicare Part D, you should enroll in Part D at 65.

You enroll in Part D at the same time you enroll in Medicare Parts A and B. When you register online or by phone, you will be asked whether you want to add Part D. If you are unsure which plan to choose, you can enroll in any plan during your Initial Enrollment Period and switch plans during the annual open enrollment period (October 15 to December 7 each year).

What to do if you missed your important date

If you are past your Initial Enrollment Period and did not have creditable coverage, you can still enroll in Medicare, but you will owe the late enrollment penalty. The penalty applies for as long as you have Medicare — it does not expire. You can enroll during the General Enrollment Period, which runs January 1 to March 31 each year. Coverage begins July 1 of that year.

Contact Medicare at 1-800-MEDICARE to enroll during the General Enrollment Period. Bring documentation of any creditable coverage you had at age 65 if you believe you may have access to for an exception. Even with a penalty, enrolling is important — Medicare covers many services that private insurance may not, and the longer you wait, the higher your total out-of-pocket costs may be.

Questions to ask your doctor or benefits counselor

Before you register, consider asking your current doctor or health plan whether they accept Medicare. Ask your employer's benefits department whether you should enroll in Part B when ready or delay.

If you have questions about which Medicare plan to choose, contact your State Health Insurance information Program (SHIP) — it offers free, unbiased counseling. Find your state's SHIP at shiptalk.org. A SHIP counselor can walk you through your options and help you understand the costs of different plans.

Frequently Asked Questions

What if I turn 65 in the middle of the month?

Your Initial Enrollment Period still runs three months before through three months after the month you turn 65, regardless of the date within that month. If you enroll before your birthday, coverage typically begins on the first day of the month you turn 65. If you enroll after your birthday, coverage usually begins the first of the following month.

Do I have to enroll in Part A if I do not think I will use it?

Yes. Part A (hospital insurance) has no monthly premium for most people, and enrolling protects you from penalties. Hospital stays are expensive, and you cannot predict when you might need one. Enrolling in Part A at 65 costs nothing and removes the risk of a penalty later.

Can I change my mind after I register?

Yes, but only during certain windows. You can switch Medicare plans during the annual open enrollment period (October 15 to December 7). If you enrolled in Part B and later discover you had creditable coverage, you may be able to disenroll and avoid the penalty — contact Medicare when ready to explain your situation.

What if I am not a U.S. citizen?

You must be a U.S. citizen or permanent resident (green card holder) for at least five years to enroll in Medicare. If you are a permanent resident, bring your green card when you register. If you do not meet these requirements, you may still work and pay Medicare taxes, but you cannot enroll until you become a citizen or meet the residency requirement.

Does my spouse need to register at the same time?

No. Each person has their own Initial Enrollment Period based on their own birthday. Your spouse registers during the seven-month window around their 65th birthday. If your spouse is younger and covered under your health plan, they can stay on your plan until they turn 65 and register for Medicare.